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Old 03-10-2006, 01:12 PM
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coelacanth coelacanth is offline
prehistoric bony fish
Location: Santa Monica, CA
 
Join Date: Jul 2005
Posts: 387
Mein Auto: 1997 Arctic Silver 540i 6
Quote:
Originally Posted by Lscman
Good search job. I see you found my post about the "primary root cause" for cat failure. Engine misfire for any other reason or fuel delivery system malfunction can cause cats to burn up. What more can I say...

If you search some more, you'll find my threads that caution 540i owners about crankcase ventilation problems. Tech Tips shows repair methods, but a thorough fix involves removal of the intake manifold to ream out vent piping. The rear cover diaphram valve clogging or failing is generally only symptomatic. Positive pressure cause the oil seals to fart and make a buzzing/whirring sound. This can really screw up your motor seals and gaskets.
Thanks for the replies.
I had a Master Tech at Bob Smith BMW check everything, and he said there were no oil leaks and that the PCV valve was OK etc.
The dealership's price of $1,515 more than I want to pay, so I think I will buy another OEM cat and have it installed at an indie shop. My service advisor at Bob Smith warned me against using non OEM cats, and I like having the OE BMW stuff on my car anyway (except for the brake pads).

Is there any negative effects on the car from driving around with a bad cat? I haven't noticed any decrease in mpg etc. Thanks.
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